The cascading multibillion-dollar cost of the celebrated F-35 stealth aircraft has prompted the federal government to "hit the reset button" on its controversial effort to replace Canada's aging fighter fleet.

Public Works Minister Rona Ambrose said Wednesday the entire process would be reviewed in the face of a long-awaited KPMG report that warns the Lockheed Martin-built F-35s could cost Canada as much as $45.8 billion over 42 years.

The report says National Defence neglected to build a large enough financial cushion into the plan, and that the paltry-by-comparison $9 billion the department set aside likely won't be enough to cover the planned purchase of 65 jets.

Ambrose and Defence Minister Peter MacKay both insisted no decision will be made until the review is complete.

"The next step is a full review of options," Ambrose told a news conference following the release of the report, which came after a question period dominated by F-35 questions.

"We have hit the reset button and are taking the time to do a complete assessment of all available options."

MacKay said the government would ensure "that balance is maintained between the military needs and taxpayer interests."

"Ultimately, our government will get the best plane for the armed forces, for our pilots and for Canadian taxpayers."

The NDP's opposition critics were unmoved, however, insisting the government was steadfastly refusing to admit the whole process has been fumbled.

"You can't move on, you can't move forward until you've admitted that you've got a problem and that you've made mistakes," said Matthew Kellway, the party's procurement critic.

"What we've heard today is that the minimum price for this plane is three times higher than anything that this government has publicly disclosed to date. That's tens of billions of dollars higher.

"What we haven't heard today is what we wanted to hear, that there will be an open competition for a replacement for the CF-18."

The KPMG report said uncertainties in the oft-delayed program could force the air force to cut the number of planes to 55 or force the Conservatives to spend more, anywhere from $1.5 billion to $2.5 billion.

The Conservatives, who have insisted the F-35 is the only available aircraft that meets Canada's specific needs, continue to insist the $9 billion ceiling is a firm one.

But the various cost figures cited in a series of reports released today are based on a number of variables, including the notion that other allied nations will buy as many jets as they've promised.